Techniques and devices for metering the various forms of electrical energy are well known. Meters, such as utility power meters, can be of two types, namely, electromechanical based meters whose output is generated by a rotating disk and electronic based meters whose output component is generated electronically. A hybrid meter also exists, wherein an electronic register for providing an electronically generated display of metered electrical energy has been combined, usually optically, to a rotating disk. Pulses generated by the rotating disk, for example by light reflected from a spot painted on the disk, are utilized to generate an electronic output signal.
It will be appreciated that electronic meters have gained considerable acceptance due to their increasing reliability and extended ambient temperature ranges of operation. Consequently, various forms of electronic based meters have been proposed which are virtually free of any moving parts. In the last ten years several meters have been proposed which include a microprocessor.
Testing of electronic meters has always been a problem. A special mode of register operation known in the industry as the test mode has been available to ease register testing, however, little has been done to improve overall meter testing. Electronic meters have the potential of providing faster test times, multiple metering functions and calibration of the meter through software adjustment. However, implementing such functions can be expensive and complicated.
Presently, electric utility companies can test mechanical meters with a piece of test equipment which can reflect light off a metered disk to detect a painted spot as the disk rotates. An alternative form of testing mechanical meters is disclosed in U.S. Pat. No. 4,600,881—LaRocca et al. which describes the formation of a hole in the disk. A light sensitive device is placed in a fixed position on one side of the disk. As the disk rotates, and the hole passes over the light sensitive device, a pulse is provided indicating disk movement.
Since electronic meters preferably do not contain rotating disks, such simple testing techniques cannot be utilized. Consequently, a need exists for an electronic meter having a relatively simple means of testing the meter.